Various tests are conducted for the purpose of eliminating newly manufactured ICs that do not meet a required specification. In a burn-in test, the products have their heat-resistant characteristics tested by operating them at certain high temperatures for a prescribed period of time so as to identify and eliminate those which do not have the required properties. In a burn-in test, the IC is mounted on a socket which has been prepared specifically for it, with the socket being mounted on a printed circuit substrate, and placed in a heating furnace.
Various kinds of sockets have been proposed for burn-in tests for IC packages of the BGA, FBGA and CSP types which have become popular in recent years. These sockets are provided with a base member of an electrical insulating material mounting a plurality of contact members that correspond to the terminals of the IC. The contact members are arranged in conformity with the terminals on the mounting surface of the IC so that, when the IC has been placed on the base member, the contact members establish electrical contact with corresponding terminals. In the case of a typical socket of this kind, a cover member, movable between open and closed positions, is provided for attaching the IC on a mounting seat with the IC being attached to or released from the mounting seat as the cover is moved to one position or the other.
With reference to FIGS. 23 and 24, a known socket has a cover 232 rotatably supported relative to a base 231. When cover 232 is opened as shown in FIG. 23, IC 100 can be placed onto a mounting seat 231a and cover 232 is then closed by an automatic mechanism, not shown in the drawing. A hook 233 engages with a catch on base 231, thereby maintaining cover 232 closed. IC 100 is held on mounting seat 231 a from above by an engagement surface 232a inside cover 232, with the IC terminals being held in contact with tips of contact members 234 that corresponds thereto.
Other types of sockets are provided with a mechanism for vertically moving the cover member relative to the base member and a latch that can be opened or closed in linkage with the movement of the cover. Generally speaking, the latch opens when the cover member is lowered, thereby making it possible for an IC to be placed on the mounting seat of the base with the latch closing and holding the IC on the mounting seat from above when the cover is raised. In any type of the sockets described above, the electrical connections of the socket to the terminals of the IC are effected by pressing of the lower part of the terminals of the IC to the tips of the contact members. If there are variations in the installed height of the terminals of the IC, however, the force of the contact members against the terminals will vary, thereby adversely affecting the reliability of the connection between some terminals and contact members. Additionally, there are some cases where the lower surfaces of the terminals of the IC are subjected to damage occasioned by pressing of the contact members against the terminals. Any damage to the lower surface of the terminals could cause soldering failure when, upon successful testing, the IC is mounted to a printed substrate.